In addition to its acquisition cost, a vehicle has operation costs that include, for example, fuel, tires, maintenance, repairs, and insurance. Vehicle owners and operators typically want to keep operation costs as low as possible, usually under the conditions that acceptable performance and safety can be attained.
Key elements of operation costs are tires, which are expensive, especially for heavy vehicles like over-the-highway trucks, and fuel, which can have many forms (e.g., gasoline, diesel fuel, hydrogen, electricity, etc.). Even small improvements in tire and fuel consumptions can have a large impact on lowering operation costs. If tires can be replaced less often, operation costs over a given time can be reduced. Fuel consumption depends on many factors, including for example engine efficiency, transmission losses, and tire characteristics. Over the years, fuel consumption has been reduced by new and more efficient oils that reduce the internal friction of the engine and transmission, by improved engine combustion that increases fuel efficiency, and by new tire tread designs and rubber compositions that reduce losses due to the tires.
A highway truck's maximum tractive force on a dry road is achieved at approximately 20% slip of the tires of the drive wheels. Prior art vehicle control systems, which include engine-torque control systems and traction control and anti-lock brake systems, aim to maximize tractive force or traction and do not address tire wear. For example, U.S. Pat. No. 5,737,713 to Ikeda et al. discloses a traction control system for adjusting engine torque based on an initial engine torque, acceleration, vehicle weight, axle weight, and gear ratio. U.S. Pat. No. 5,278,761 to Ander et al. discloses a method for vehicular wheel-spin control that adapts to different road traction characteristics, with the system adjusting engine torque in response to sensed conditions, including vehicle weight. U.S. Pat. No. 4,985,838 to Hashiguchi et al. discloses a traction control system for limiting engine torque based on vehicle weight, wheel speed, engine RPM, and transmission status. U.S. Pat. No. 4,964,045 to Iwata et al. discloses a traction control system associated with a vehicular brake system which can control braking force for respective individual driving wheels independently of each other on the basis of an average wheel slippage data. Engine torque may also be controlled.
There is room for improvement in controlling a vehicle to lower operation costs, especially for heavy vehicles.